Transmissible spongiform encephalopathy (TSE) is known as a neuro-degenerative disorder causing serious degeneration of neurons and includes, for example, bovine spongiform encephalopathy (BSE), scrapie, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome, Kuru, transmissible mink encephalopathy, chronic wasting disease, feline spongiform encephalopathy, etc. which often affect humans and animals. In the case of BSE, the linkage to vCJD which is a human form of BSE has been reported.
The causative agent of TSE does not have immunogenicity while having relatively long incubation period. From a histopathological examination of BSE affected bovine brain tissue, it was demonstrated that disease-related spongiosis was generated due to damage of nerve cells and deposition of abnormal protein fibers.
A causative agent of TSE is an infectious protein called an abnormal prion. Contrary to typical viruses requiring nucleic acid, the abnormal prion contains no nucleic acid but consists of protein alone. Regarding TSE, it has been reported that, when an abnormal prion (PrPsc) as an infectious agent is combined with a normal prion (PrPc), the combined material is transformed into a pathogenic prion, in turn being accumulated in brain tissue (Prusiner 1989). A serious problem is that a tissue infected with such a pathogenic prion, that is, PrPsc may also infect cells and, when inoculating an animal with the infected cells, a prion disease may be derived. Accordingly, we believe that, if a specific cell susceptible to the prion disease is developed, this cell may be advantageous for a variety of studies, for example, screening of anti-prion substances, formation and inhibition of pathogenic prions, a biological marker for diagnosis of the prion disease, and the like.